It has been a conventional practice to flow streams of heat-softened glass from a stream feeder, bushing or substrate, and flooding of the glass on the surface of the stream feeder, bushing or substrate has presented difficulties. Glass flooding occurs occasionally on a stream feeder surface where the glass flow orifices are in depending projections or tips on the feeder surface. Flooding most always occurs when a filament breaks as it is being attenuated or pulled from a tipless bushing or orifice plate of a bushing wherein the stream flow orifices are merely openings in the orifice plate. Removing the "flood" can be a difficult and time-consuming effort.
In processes wherein glass streams are attenuated to fibers or continuous filaments the trend is toward the utilization of a stream feeder, bushing or substrate having a floor section or orifice plate provided with stream flow orifices without depending projections or tips. The use of an orifice plate without depending orificed projections enables the stream flow orifices to be more closely spaced which permits a substantial increase in the number of glass streams flowing from a feeder or bushing than is possible with a feeder or bushing having orificed projections.
Even when the glass constituting the flood is removed by conventional means such as a tool or bushing pick and fiber separation achieved, a residual thin layer of molten glass usually remains on the feeder floor tip section or orifice plate surface. Such thin layer of residual glass is undesirable because the emissivity of the molten glass layer introduces a radiation change relative to the radiated energy which would leave the surface if the thin glass layer were not on the surface. Furthermore, a residual film or layer of molten glass contributes to or fosters reflooding of the area because the surface is already "wetted" by the glass.
Carbon and/or graphite are known to be good nonwettable materials with respect to molten glass but they are fugitive and the carbon on the surface of a stream feeder or bushing is not permanent because of sublimation and/or oxidation to carbon dioxide at feeder or bushing temperatures. Up to the present time there has been no completely successful and economical means for removing a glass flood once formed on a stream feeder floor or orifice plate surface.
Methods have been devised for the purpose of preventing glass flooding of a stream flow section or orifice plate of a stream feeder or bushing but such methods are costly as they utilize an inert environment provided by a continuous flow of inert or nonoxidizing gas and a continuous flow of decomposable carbonaceous gas or other method employing continuous flow of a gas or gases.
For example, the United States patent to Russell No. 3,829,301 discloses a method wherein a hydrocarbon gas is decomposed to form hydrogen and carbon which prevent wetting of a stream feeder surface by molten glass.
Another method is disclosed in the U.S. Pat. to Veazie No. 3,989,494 for preventing flooding of glass which involves partial burning or combusting a combustible carbonaceous gas providing a reducing or luminous flame resulting from incomplete combustion of the gas whereby the flame yields particles of carbon effective at the surface of a stream feeder to prevent flooding.
A method has been proposed wherein glass streams flow from an orifice plate, the plate having porous regions supplied with gas delivered from the pores in the plate to prevent flooding of the glass on the surface. This method is disclosed in Russell U.S. Pat. No. 3,716,116.
In these above-described methods, the gases are supplied continuously and are for the purpose of preventing flooding of glass occurring on a surface of a stream feeder, bushing or substrate.